This invention relates generally to a multi-story concrete slab construction system and method, and more particularly to such systems and methods wherein the upper story concrete slabs are poured in place to form the upper story floors and the framing elements are metal posts and beams that support horizontally extensive decking to receive the wet concrete.
It is well known to construct multi-story buildings utilizing concrete floors supported by an interconnected framework of either metal or concrete vertical post members and horizontal beam members. One methodology for constructing such buildings comprises the manufacture of prefabricated concrete slabs. The cured concrete slabs, typically manufactured off-site and transported to the building site, are lifted into position using cranes. The prefabricated slabs are usually provided with embedded connector means such that the slabs may be joined to the framework by mechanical fasteners, welding or similar methods. Examples of various systems using this methodology can be seen in U.S. Pat. No. 3,110,982 to Besinger, U.S. Pat. No. 3,378,971 to Singer et al., U.S. Pat. No. 3,594,971 to Hughes, U.S. Pat. No. 3,824,750 to Antoniou, U.S. Pat. No. 4,081,936 to Wise, U.S. Pat. No. 4,100,713 to Shoe, U.S. Pat. No. 4,330,970 to Bonink, U.S. Pat. No. 5,737,895 to Perrin, and U.S. Pat. No. 6,151,851 to Carter. While this type of construction has proven to be a successful approach, there are inherent drawbacks or problems. For example, off-site production of the prefabricated concrete slabs requires a separate production facility and the slabs must be transported to the building site. Cranes must be utilized to remove the slabs from the transport trucks and to position the slabs within the framework, which is inherently dangerous due to the size and weight of the concrete slabs. Securing the slabs to the framework requires many man-hours of labor. All of these factors contribute to lengthening the time of construction for even relatively simple multi-story buildings.
To address these and other problems encountered in the use of prefabricated concreter slabs for multi-story building construction, systems and methods have been developed whereby the upper level floors are poured in place one floor at a time on horizontally extending decking retained by the post and beam framework. The posts, beams and decking are erected for a first upper level floor, and the concrete is poured. The wet concrete is screeded either mechanically or by hand to provide the desired finish or upper surface. Upon curing, the posts, beams and decking for the next upper level floor are erected, the concrete is poured, finished and allowed to harden, and the next level is then erected. With this method a large number or even all the posts on a floor are joined horizontally by a monolithic concrete slab, thereby crating a laterally stabilized and rigid structure.
An example of this method is shown in U.S. Pat. No. 4,074,487 to Daniels et al. In this system, vertical load bearing members having triangular brace members are joined with horizontal joist members. The upper ends of the vertical posts comprise a male connector member. Support decking is then positioned on the joists with a portion of the vertical posts and the connector member extending above the decking. The concrete floor is then poured on the decking with only the connector members extending above the surface of the concrete. Once the concrete has cured, the next level of vertical posts is erected by inserting their lower ends on to the exposed connector members, and the process is repeated. The main problem with this poured-in-place method is that the connector members extend above the surface of the concrete and therefore care must be taken to cover the connector members or to otherwise insure that no concrete is deposited onto the connector members. The exposed connector members interfere with the screeding operations necessary to finish the surface of each floor and thereby significantly increase the man-hours necessary to complete each floor.
U.S. Pat. No. 5,444,957 to Roberts shows an alternate system for constructing a multi-story building using poured-in-place concrete floors that addresses the problem of the exposed connector members on the vertical posts. In the Roberts system, the top of the lower post member is provided with a horizontal flange or plate. Threaded bolts are inserted upwardly through the flange such that the threaded ends are positioned above the flange, with the bolts extending above the flange a distance sufficient to receive a bottom flange on the upper post to be supported as well as the securing nuts. The slab is then poured to a depth that completely covers the upper ends of the threaded bolts. Upon curing, the concrete situated above the flange on each post must be chipped away down to the flange, and the upper surface of the flange and the threaded bolts must be cleaned so that the upper posts can be positioned onto the lower posts and secured. This chipping and cleaning operation is labor and time intensive and may result in damage to the threaded bolts. In addition, since the head of the bolts are located beneath the flange and within the poured concrete, either the bolts must be individually welded to the underside of the flange or great care must be taken to insure that the bolt head is completely embedded within the concrete and that the concrete is completely cured prior to tightening of the nuts. If the bolt heads are not sufficiently restrained from turning, the bolts will rotate when the nuts are turned to secure the upper posts to the lower posts and there will be no way to correct this deficiency without chipping into the slab from the underside. Also, the chipping required to expose the bolts and flanges result in an unsightly crater surrounding each post, which must be filled in or covered.
It is therefore an object of this invention to provide a poured-in-place system and method for constructing upper level floors in multi-story buildings that addresses the problems and inefficiencies of the known methods and systems. It is an object of this invention to provide such a system and method whereby the vertical posts, horizontal beams and decking can be erected and the concrete poured such that the upper ends of the posts do not extend above the upper surface of the concrete slab, thereby allowing the slab to be easily screeded and finished. It is a further object to provide such a system and method whereby upon curing of the concrete slab the vertical posts of the next level are quickly and easily aligned onto the lower posts and secured by welding such that the support framework for the next floor level can be erected, and the procedure repeated as required to finish the multi-story building. These objects, as well as objects not expressly set forth, will be supported by and made clear from the disclosure set forth below.